1. Field of the Invention
The present invention relates to a magnetoresistance effect device composed of a magnetic multi-layer film having giant magnetoresistance effect, a magnetic head therewith, a magnetic recording/reproducing head therewith, and a magnetic storing apparatus therewith.
2. Description of the Related Art
In magnetic recording apparatuses such as a HDD (Hard Disk Drive), the record track width is being decreased so as to increase the record density. To compensate the decrease of the reproduced output due to the decrease of the record track width, a magnetic head having a high sensitive magnetoresistance effect device (MR device) is being required. In particular, an MR head having a spin valve film with giant magnetoresistance effect is hopeful as a successor. The spin valve film is composed of a magnetic multi-layer having a ferromagnetic film whose magnetization rotates corresponding to a signal magnetic field (this film is hereinafter referred to as a magnetization free layer), a non-magnetic film, a ferromagnetic film whose magnetization is fixed with a bias magnetic field of an antiferromagnetic film (this ferromagnetic film is hereinafter referred to as a fixed magnetization layer), and an antiferromagnetic layer that fixes the magnetization of the fixed magnetization layer.
In an MR head having the spin valve film, there are large practical problems of Barkhausen noise causes by a magnetic domain wall of the magnetization free layer and a reproduction fringe in the vicinity of both edge portions of a reproduction track. To solve these problems, as shown a cross section diagram viewed from direction opposite to a medium in FIG. 12, a so-called abutted junction type MR head of which outer portions of both edge portions 1a and 1a of a record track width of a spin valve film 1 are etched out and instead hard magnetic films 2 are disposed thereto has been proposed.
The spin valve film 1 shown in FIG. 12 has a magnetization free layer 4, a non-magnetic film 5, a fixed magnetization layer 6, and an antiferromagnetic film 7 that are formed in the order on a substrate 3. In addition, a pair of electrodes (reproduction electrodes) 8 that supply a sense current to the spin valve film 1 are formed on the hard magnetic film 2.
In the MR head of abutted junction type shown in FIG. 12, a bias magnetic field of the hard magnetic film 2 causes a magnetic domain of the magnetization free layer 4 to disappear, thereby suppressing Barkhausen noise. In addition, since a portion other than the record track width is substituted with the hard magnetic film 2, only record information can be read from record track. Thus, the reproduction fringe can be remarkably reduced.
However, the MR head having the spin valve film 1 of the abutted junction type has the following problems. Firstly, a gap film (not shown) composed of a non-magnetic insulator such as alumina is disposed below the spin valve film 1. Thus, the reproduction electrode 8 and the hard magnetic film 2 contact a wall surface of the spin valve film 1 that has been etched out. Consequently, the contact resistance increases or becomes unstable.
Secondly, when the magnetization free layer 4 at both the edge portions of the spin valve film 1 is etched out, since the magnetization free layer 4 is disposed at the bottom position, the gap film tends to be excessively etched out. Thus, an insulation defect of a magnetic shield layer disposed below the gap film tends to take place.
Thirdly, when the spin valve film is etched out, the lower portion of the spin valve film 1 is lesser tapered than the upper portion thereof. Thus, an exchange-coupled region of the hard magnetization film 2 and the magnetization free layer 4 increases in the taper portion. In the taper portion, since the exchange-coupled force is unstable, Barkhausen noise tends to take place.
Fourthly, since the edge wall surface of the hard magnetic film 2 inevitably contacts the edge wall surface of the fixed magnetization layer 6, the bias magnetic field of the hard magnetic film 2 is applied to the fixed magnetization layer 6. Thus, the magnetization of the fixed magnetization layer 6 to be fixed in the direction of the width of the spin valve film 1 (in the direction to which the signal magnetic field is applied) is inclined to the direction of the bias of the hard magnetic film 2 (the longitudinal direction of the spin valve film 1). Consequently, a good linear response to the signal magnetic field can not be obtained.
In addition, another MR head has been proposed. In this MR head, a bias magnetic field applying film such as a hard magnetic film and an antiferromagnetic film is directly layered on edge portions of an MR film so as to exchange-couple them. Thus, Barkhausen noise is removed. However, in the conventional spin valve film of which a fixed magnetization layer or the like is disposed on a magnetization free layer, a hard magnetic film and an antiferromagnetic film should be disposed on the substrate side. When these films are patterned, the surface characteristic of a base film of the spin valve film deteriorates.
In particular, to stably exchange-couple the hard magnetic film and the antiferromagnetic film with the magnetization free layer, the film thickness of the hard magnetic film and the antiferromagnetic film should be increased. In the case that these films are thick, when they are patterned, the surface characteristic of the base layer of the spin valve film inevitably deteriorates. In addition, with the antiferromagnetic film, it is difficult to obtain a strong exchange bias. With the hard magnetic film, coercive force decreases due to the reaction of the magnetization free layer. Thus, the magnetization cannot be stably fixed at the edge portions of the track width. Consequently, the decrease of reproduction fringe and the suppression of Barkhausen noise are insufficient.
As described above, with the MR head having the conventional spin valve of the abutted junction type, the contact resistance increases or becomes unstable due to the shape thereof. Insulation defect and unstable exchange coupling of the hard magnetic film and magnetization free layer tend to take place. In addition, since the magnetization of the fixed magnetization layer is inclined, a good linear response to a signal magnetic field cannot be obtained.
On the other hand, with the MR head of which the bias magnetic field applying film such as a hard magnetic film and an antiferromagnetic film is directly layered on a spin valve film, the surface characteristic of the base film of the spin valve film deteriorates. Moreover, the magnetization cannot be stably fixed at the edge portions of the track width. Thus, the decrease of reproduction fringe and the suppression of Barkhausen noise are insufficient.
Furthermore, a magnetic storing apparatus such as a magnetoresistance effect random access memory (MRAM) having a spin valve film has been studied. In this case, a sufficient bias is required.
Thus, an object of the present invention is to provide a magnetoresistance effect device that suppresses reproduction fringe and Barkhausen noise and that accomplishes the decrease of contact resistance, suppression of insulation defect, and good linear response. Another object of the present invention is provide a magnetic head having the magnetoresistance effect device so as to improve characteristics, a magnetic recording/reproducing head thereof, and a magnetic storing apparatus thereof.
A first aspect of the present invention is a magnetoresistance effect device, comprising a substrate having a main surface, a magnetoresistance effect film composed of a magnetic multi-layer film having at least an antiferromagnetic film, a first ferromagnetic film, a non-magnetic film, and a second ferromagnetic film formed in the order above the main surface portion of the substrate, the magnetic multi-layer film having giant magnetoresistance effect, the second ferromagnetic film disposed in a magnetic field detecting portion, a pair of bias magnetic field applying films adjacent to the both edge portions of the magnetic field detecting portion, the bias magnetic field applying films disposed on a conductive film selected from the group consisting of the antiferromagnetic film, the first ferromagnetic film, and the non-magnetic film, and a pair of electrodes for supplying a current to the magnetoresistance effect film.
A second aspect of the present invention is a magnetoresistance effect device, comprising a substrate having a main surface, a magnetoresistance effect film composed of a magnetic multi-layer film having at least an antiferromagnetic film, a first ferromagnetic film, a non-magnetic film, and a second ferromagnetic film formed in the order above the main surface of the substrate, the magnetic multi-layer film having giant magnetoresistance effect, the second ferromagnetic film having a first portion corresponding to a magnetic field detecting portion and a second portion corresponding to outer portions of both edge portions of the magnetic field detecting portion, the film thickness of the second portion being smaller than the film thickness of the first portion, a pair of bias magnetic field applying films disposed on the second ferromagnetic film at the outer portions of both the edge portions of the magnetic field detecting portion, and a pair of electrodes for supplying a current to the magnetoresistance effect films.
A third aspect of the present invention is a magnetoresistance effect device, comprising a substrate having a main surface, a magnetoresistance effect film composed of a magnetic multi-layer film having at least an antiferromagnetic film, a first ferromagnetic film, a non-magnetic film, and a second ferromagnetic film formed in the order above the main surface of the substrate, the magnetic multi-layer film having giant magnetoresistance effect, the magnetoresistance effect film having a magnetic field detecting portion, a pair of bias magnetic field applying films formed on the second ferromagnetic film at outer portions of both edge portions of the magnetic field detecting portion of the magnetoresistance effect film, and a pair of electrodes for supplying a current to the magnetoresistance effect film.
A fourth aspect of the present invention is a magnetic head, comprising a lower magnetic shield layer, the magnetoresistance effect device of the present invention, said magnetoresistance effect device being formed on said lower magnetic shield layer through a lower reproduction magnetic gap, and an upper magnetic shield layer formed on the magnetoresistance effect device through an upper reproduction magnetic gap.
A fifth aspect of the present invention is a magnetic recording/reproducing head, comprising a reproducing head having the magnetoresistance effect head of the present invention, and recording head having a lower magnetic pole in common with the lower magnetic shield layer of the magnetoresistance effect head, a record magnetic gap formed on the lower magnetic pole, and an upper magnetic pole formed on the record magnetic gap.
A sixth aspect of the present invention is a magnetic storing apparatus, comprising the magnetoresistance effect device of the present invention, a write electrode for storing information to a magnetoresistance effect film of the magnetoresistance effect device, and a read electrode, composed of an electrode of the magnetoresistance effect device, for reproducing information stored in the magnetoresistance effect film.
According to the magnetoresistance effect device of the first aspect of the present invention, the first ferromagnetic film is disposed on the substrate side. The antiferromagnetic film applies a bias magnetic field to the first ferromagnetic film so as to fix the magnetization thereof. The second ferromagnetic films are disposed as the magnetization free layers on the opposite side of the substrate. Thus, the second ferromagnetic films on the outer portions of both the edge portions of the magnetic field detecting portion are removed. Consequently, a good off-track characteristic (low reproduction fringe) is obtained. In addition, a part of a conductive film of the magnetic multi-layer film is left at the outer portions of both the edge portions of the magnetic field detecting portion (reproduction track) is accomplished. Thus, an electric contact can be secured.
In addition, since a taper region that causes the antiferromagnetic film and the second ferromagnetic film to be unstably exchange-coupled can be decreased, Barkhausen noise can be stably suppressed. Moreover, a bias magnetic field can be applied to the second ferromagnetic film without need to contact the edge wall surfaces of the edge portions of the first ferromagnetic film that is the fixed magnetization layer with the bias magnetic field applying film. Thus, in addition to suppressing Barkhausen noise, a good linear response characteristic can be obtained.
According to the magnetoresistance effect head of the second aspect of the present invention, the first ferromagnetic film is disposed on the substrate side. The antiferromagnetic film applies a bias magnetic field to the first ferromagnetic film so as to fix the magnetization thereof. The second ferromagnetic films are disposed as the magnetization free layers on the opposite side of the substrate. Thus, when the bias magnetic field applying film is patterned, the surface characteristic of the base film of the spin valve film does not deteriorate. Consequently, stable characteristics of the spin valve film can be accomplished.
In addition, the film thickness of the second ferromagnetic film at the outer portions of both the edge portions of the magnetic field detecting portion is smaller than the film thickness of the second ferromagnetic film at the magnetic field detecting portion. Thus, with the bias magnetic field applying films composed of an antiferromagnetic film, the increase of exchange bias force can be expected. On the other hand, with the bias magnetic field applying films composed of a hard magnetic film, the increase of coercive force can be expected. Consequently, the magnetization of the second ferromagnetic film at the outer portions of both the edge portions of the magnetic field detecting portion is more stably fixed. Thus, in addition to suppressing Barkhausen noise, a good off-track characteristic (low reproduction fringe) can be obtained. Moreover, since the direction of the magnetization of the first ferromagnetic film that is the fixed magnetization film is not disturbed, a good linear response characteristic can be accomplished.
According to the magnetoresistance effect head of the third aspect of the present invention, the first ferromagnetic film is disposed on the substrate side. The antiferromagnetic film applies a bias magnetic field to the first ferromagnetic film so as to fix the magnetization thereof. The second ferromagnetic films are disposed as the magnetization free layers on the opposite side of the substrate. Thus, when the bias magnetic field applying film is patterned, the surface characteristic of the base film of the spin valve film does not deteriorate. Consequently, stable characteristics of the spin valve film can be accomplished.
In addition, since the film thickness of the second ferromagnetic film is decreased, with the bias magnetic field applying film composed of an antiferromagnetic film, the increase of the exchange bias force can be expected. On the other hand, with the bias magnetic field applying film composed of a hard magnetic film, the increase of the coercive force can be expected. Thus, the magnetization of the second ferromagnetic film at the outer portions of both the edge portions of the magnetic field detecting portion is stably fixed. Consequently, in addition to suppressing Barkhausen noise, a good off-track characteristic (low reproduction fringe) can be obtained. Moreover, since the direction of the magnetization of the first ferromagnetic film that is the fixed magnetization layer is not disturbed, a good linear response characteristic can be accomplished.